I had had this problem for weeks but it got worst in the last few days. It happens rqndomly. Sometimes I can play games for hours without nothing happening and sometimes it crashes just while browsing. The screen goes black(no signal), the music keeps playing for maybe 5-10 seconds and the fans start going crazy(my computer is always a bit loud). Then the sound freezes and I have a reboot. I have an i5-2500k, gtx 670and a Cheiftec 500w psu. The motherboard is a gigabyt p67-ds3-b3